Police have yet to identify the shooter or his motive in an attack Friday that killed four people and wounded five more in Santa Monica, Calif. The attacker was wearing SWAT-type gear and firing an assault rifle.

Santa Monica College students wait for police clearance to pick up their vehicles after a shooting on campus Friday in Santa Monica, Calif. A gunman with an assault-style rifle killed four and wounded five people.

A semi-automatic assault rifle is again being tied to a US mass shooting, this one a chaotic series of events led by a body-armor-clad man who killed four and wounded five people before being shot and killed by police in a college library in the iconic beachside city of Santa Monica, Calif.

The attack marked the first major mass shooting since a bipartisan gun control bill failed in the US Senate in April. The shooting may help efforts to revive the debate about gun control, as well as put focus on ongoing legislative action in some states around allowing students and faculty to carry weapons on campuses to help thwart active shooters who target what are usually so-called “gun free” zones.

The rampage began with a house fire where two victims, believed to be the gunman’s father and brother, were later found dead. Next came a violent carjacking in which one woman was shot but survived, and ended with two more people dead, including a college student.

Witnesses describe seeing a man all in black SWAT-gear waving and shooting an AR-15 rifle, the same style of weapon used by shooters in recent mass shootings in Aurora, Colo., and Newtown, Conn. Some witnesses thought the man was a policeman because of his confident gestures in stopping cars, while others described a calm, methodical attack where the shooter casually took aim and fired at targets ranging from people to buses to police cars.

Eyewitness Joe Orcutt told the Associated Press that the shooter “was just standing there, like he’s modeling for some ammo magazine. He was very calm … panning around, seeing who he could shoot, one bullet at a time, like target practice.”

To add to the tension, President Obama was in Santa Monica for a fundraising event about three miles from where the shootings took place. The incident did not affect the President’s plans, beyond a reroute of his exit.

So far, police have suggested no motive for the mass shooting.

AR-15s and other semi-automatic rifles are used in far fewer homicides than hand guns, but have become symbolic of America’s struggle to contain violent and public mass shootings. They’re immensely popular because of their ease-of-use, accuracy and customizability. Critics argue that the rifles are designed to be militaristic and offensive. Fans of the guns say they have no more lethality than a standard hunting rifle.

According to a report in Mother Jones magazine, 25 of 62 mass shootings since 1982 have occurred in the last seven years, with a record seven taking place last year. A mass shooting is defined as an event where more than four people die at the hands of a lone gun man attacking in a public place.

After jumping into a car and ordering a woman to drive, the gunman in Santa Monica opened fire on a city bus, injuring three people. In all, police are investigating nine separate crime scenes that resulted from the chaotic attack.

After the carjacking, the man apparently told the woman to drive him to Santa Monica College, a sprawling campus of some 34,000 students about a mile inland from the Santa Monica Pier. There a witness described a man in his 20s with corn rows in his hair taking aim and firing at random people and vehicles, before engaging in a gun battle with police inside a college library where students were cramming for exams.